1. Field of the Invention
The present invention relates to a device for detecting matters printed with infrared ray reflective and absorptive ink, particularly to a device for improving a quality control of a printing press for printing matters with infrared ink against forgery.
2. Prior Art
Recently, technique and skill of a color copy machine and a color DTP are rapidly developed and spread. A technical level of a printing skill is remarkably advanced. Such a trend has promoted a menace of forgery of printed matters such as securities (herein after, it is referred as "securities printed matter") and the menace becomes a serious problem.
On the other hand, in a circumstance of circulating securities printed matters, automatic vending machines and ATMs are spread and a trend of processing money with machines and/or computers by stores and banks has been promoted.
Conventionally, as an anti-forgery method, a main pattern of a securities printed matter is formed of an image with a relief formed by deeply engraved and fine and sharp minute picture lines by an intaglio printing press and a pattern of a ground tint is printed by an offset printing having a fine multi-printing accuracy. A watermark and a safe thread are provided in a sheet of a securities printed matter.
However, a technique of reproducing images is remarkably developed and a money treatment is apt to be automated. It is required to produce securities printed matters with the newest technique against forgery in addition to the conventional technique.
A technique of infrared ray ink is utilized to improve anti-forgery characteristics of securities printed matters by concealing an image printed with the infrared ray ink on the securities printed matters such as securities. Generally, ink that reflects and absorbs near infrared ray is used for printing securities.
Combining ink having the different characteristics produces such ink. The ink have the same reflective and absorptive characteristics in a visible ray region and different reflective and absorptive characteristics in an infrared ray region, respectively.
When printed matters produced by the above technique are shown through an infrared ray image converter capable of converting infrared ray to a visible ray, a shown image is different from an image shown through the naked eyes.
This method can prove that a detected securities printed matter is real. Unless the detected securities printed matter is real, the above phenomenon can not occur.
The quality of securities printed matters, printed with infrared ray reflective and absorptive ink, can not be detected through naked eyes under room light in the production process. For example, in a case where a person determines whether or not the ink is used for printing is correct, patterns are not mixed, and ink is not pale by sampling, the person must pick up some samples and check the printing quality by using an infrared ray image converter placed on a fixed place away from the printing press, while the printing press is working.
However, such a check takes a long time and it is a lazy work.
In view of importance of anti-forgery, this sample checking system is not completely safe.
Particularly, each securities printed matter is usually checked one by one in a negotiation. In a printing process, quality assurance of printed matters is also highly required.
The present invention has been accomplished to resolve the foregoing drawbacks, and the object of the present invention is to provide a highly reliable detecting device by improving quality assurance of matters printed with infrared ray ink in printing and detecting processes.